An appeals court that’s hearing a legal challenge to special counsel Robert Mueller’s authority requested Friday that the parties involved file briefings on how the takeover of acting Attorney General Matt Whitaker — who’s taking charge of the probe with the Wednesday firing of Attorney General Jeff Session — may impact the case.

“It is ORDERED by the Court on its own motion that each party submit a supplemental brief addressing what, if any, effect the November 7, 2018 designation of an acting Attorney General different from the official who appointed Special Counsel Mueller has on this case,” the order says, giving the parties a deadline of Nov. 19.

The appeals court panel heard oral arguments on the case on Thursday, during which the judges said that it should be argued as if the shake-up at the Justice Department hadn’t happened, but indicated that they were likely to ask for briefing on the change of leadership.

The challenge has been brought by Andrew Miller, an ex-Roger Stone aide who argues that Mueller’s appointment was unconstitutional because it was made by Deputy Attorney General Rod Rosenstein — who had oversight over the federal Russia investigation because Sessions was recused — rather than by the attorney general.

Miller’s lawyer Paul Kamenar (pictured above) told reporters after the hearing that he believes that Sessions’ replacement, Whitaker, has the authority to reappoint Mueller if he chooses, but argued that everything Mueller had done before that point — including indictments and plea deals — should be invalidated due to what Kamenar says is a lack of authority.

Whitaker, notably, has shown himself to be a deep skeptic of the Russia investigation in punditry he did before joining the Justice Department as Sessions’ chief of staff last year.

Four federal judges have upheld Mueller’s authority, including U.S. District Court Chief Judge Beryl Howell, who rejected Miller’s arguments and held him in contempt for resisting a Mueller subpoena. (She has paused the contempt decision while he appeals the case).

Miller’s lawyer told reporters Thursday that if they lose at the appeals court level, they intend to appeal the case to the Supreme Court.